Process of ripening a cellulose ester and the product thereof



Patented July 4, 1933 UNITED" STATES PATENT OFFICE GEORGE soHNnInEn, or .MONTCLAIR, JERSEY, ASSIGNOR To CELA'NESE CORPORATION or AMERICA, A CORPORATION or DELAWARE PROCESS OF RIPENING- A OELLULOSE ES TER AND THE PRODUCT THEREOF No Drawing. Original application filed November 5, 1927', Serial No. 231,397.

application filed-July 2, 1930. Serial No. 465,447.

acetate and relates more particularly to the so called ripening operation wherein the solubility characteristics of the cellulose esters are modified.

This application isadivislon of my prior application 231,397 filed Nov. 5, 1927.

An. object of my invention is to provide a method of ripening, hydrolyzing or modifying the solubility characteristics of cellulose acetate or other organic esters of cellulose.

Further objects of my invention will appear from the following detailed description.

According to the present invention improved products are obtained by effecting the ripening in two stages, in the first of which the ripening agent is added to the acetylation or esterification mixture and the whole allowed to stand until the cellulose ester is partially ripened, and in the second stage the product precipitated from the first stage is further ripened in the presence of dilute acid. By this means I have found that degradation of the cellulose molecule is reduced to a minimum, and in addition products are obtained which are very Valuable, particularly for incorporation in lacquers.

The following example shows amethod of carrying out my invention. The actual method of esterification used in this example is designed to produce a cellulose ester of low viscosity characteristics, however the method of ripening or hydrolyzing is'equally applicable to the production of other organic esters of cellulose.

Example 100 parts of cotton linters, wood pulp or reconstituted cellulose with or-without previous preparation, such as activation with acids and or alkalies, are added to a mixture of 300 to 400 parts of acetic anhydride and 300 to 400 parts of acetic acid containing from 10 to 15 parts of sulphuric acid. The temperature to which this mixture is cooled before the cellulose is added is determined by experimentwith the particular cellulose used, so that the maximum temperature reached in is: I I p 1, In the process of partially hydrolyzing Divided and this thereact-ion does'not exceed 50. to 55 O. Afterthis point has been reached the temperature is maintained between about 40 to 55? C. for about 2 hours or longer depending somewhat on the nature of thecellulose used. The mass is then lowered to a ripening tem perature of below 20 to C. and a small quantity of water (say fronrlO to parts), or water containing acetic acid and/or by drogcn peroxide is added for ripening in the usual manner. The ripening is interrupted by precipitating the mass with water at a stage when a sample is soluble in hotchloro form and'soluble in hot mixture of equal parts of alcohol and benzenecontaining a small amount of water. From the solubility properties it is evident that the cellulose acetate has undergone only a mild hydrolysis. The precipitated product is then subjected to ripening in the presence of dilute acid. At the completion of this ripening the product displays a very slight plasticity in hot chloroform and is soluble in ahot mixture of equal parts of alcohol and benzenewithout the addition of any water and is soluble in various other organic solvents, such as acetone, methyl acetate etc.

In a similar manner cellulose formate, formed by the use of formic acid in the esterification, or cellulose propionate or butyrate formed with the aid of a correspondingorganic acid anhydride, or other organic esters of cellulose may be ripened.

It is to be understood that the foregoing detailed description is given merely by way of illustration and that many variations may be made therein without departing from the V spirit of this invention.

Having described my invention what I claim and desire to secure by Letters Patent cellulose acetate, conducting the operation in two stages, in the first of which thereis added to the liquid product of acetylation a quantity of water sufficient to produce a mild hydrolysis and when this hydrolysis has occurred the acetateis precipitated by adding'much water, while in the second stage the precipiacetic anhydride, adding a small proportion of water to the reaction mixture, allowing the mixture to stand until the cellulose acetate is partially ripened, precipitating the cellulose I acetate by the addition of water, and completing the ripening of the cellulose acetate in the presence of weak acid.

4. In a process for the production of cellulose acetate as claimed in claim 8, so conducting the ripening operation that the end product exhibits only a slight or very slight plasticity in hot chloroform and is soluble in acetone, methyl acetate anda mixture of alcohol and benzene. I

5. Process for producing and treating organic esters of cellulose comprising esterifying cellulose and after completion of esterification adding a ripening agent to the reacand after completion of esterification adding a ripening agent to the reaction mixture and permitting the same to stand until the cellulose acetate is partially ripened, separating the cellulose acetate and completing the ripening inpresence of dilute acid.

7. Organic esters of cellulose which have been partiallyhydrolyzed in two stages, in r the first of which there is added to the liquid product of esterification a quantity of water to produce a mild hydrolysis and in the second stage the organic ester of cellulose is further hydrolyzed by treatment with dilute acid.

8. Cellulose acetate which has been partially hydrolyzed in two stages, in the first of which there is added to the liquid product of esterification a quantity of water to produce a mild hydrolysis and in the second stage the cellulose acetate is further hydrolyzed by treatment with dilute acid.

In testimonywhereof, I have hereunto subscribed my name. 7

- GEORGE SCHNEIDER. 

